The present invention relates generally to plasma arc torches and more particularly to devices and methods for controlling the flow of a working gas to a plasma arc torch.
Plasma arc torches are commonly used for cutting, marking, gouging, and welding metal workpieces by directing a high energy plasma stream consisting of ionized gas particles toward a workpiece. The plasma arc torch is typically connected to a power supply that provides both gas and electric power for operation of the plasma arc torch and is operable through a trigger disposed within a torch handle for activation of the gas and the electric power. With plasma arc torches of the known art, the trigger operates both the gas and the electric power such that neither the gas nor the electric power are controlled separately local to the torch handle. Some known art plasma arc torches provide separate gas controls, however, the controls are disposed within the power supply or at a location remote from the operator.
Activation of gas flow only, i.e. no electric power, is often advantageous in certain applications such as for cooling torch parts or the workpiece. However, many plasma arc devices do not provide for a gas only mode of operation, and those that do provide for such a mode require the operator to initiate and terminate the gas flow at the power supply, or at another remote location, not local to the plasma arc torch where operations are being performed. As a result, operation of a gas only mode is relatively time consuming and cumbersome in plasma arc torch systems of the known art.
Additionally, with plasma arc torches of the known art, a few seconds typically elapse from the time an operator engages a trigger to when a plasma stream is generated, which is a function of the amount of time required for the gas to travel from the power supply, through the torch lead, and to the torch head. Accordingly, with longer torch leads, the restart times are correspondingly longer, which results in further delays that reduce work efficiency and that can become frustrating to an operator if the torch is shut off and re-ignited on a regular basis. In one known system, a gas control valve is provided that dissipates gas in a plasma arc chamber after a plasma arc has been extinguished. However, the gas must still travel the length of a torch lead and rise gradually in accordance with the teachings of the known system.
Accordingly, a need remains in the art for a device and method that more efficiently controls the flow of gas to a plasma arc torch. A further need exists for such a device and associated method that reduces restart times, that is relatively simple to operate, and that does not require significant manual dexterity of the operator.
In one preferred form, the present invention provides a plasma arc torch that comprises a torch handle, a torch head disposed within the torch handle, a torch lead operable with the torch head, a gas control device disposed within the torch handle and operable with the torch lead and the torch head, and an activation member operable with the gas control device. Accordingly, the activation member activates the gas control device such that gas flow is supplied from the torch lead to the torch head, and the activation member deactivates the gas control device such that the gas flow is terminated local to the torch handle. Several forms of the activation member are provided, which may comprise a trigger system, a button, or a safety member, among others. Similarly, several forms of the gas control device are provided, which may comprise a gas control valve or a switch that activates a separate gas control device disposed within a power supply, among others. In another form, a gas control device is provided local to the torch handle so that gas at operating pressure is available adjacent the torch head such that restart times are reduced.
Additionally, methods of operating the plasma arc torch to provide a supply of gas local to the torch handle are provided by the present invention. The methods generally comprise operating the gas control device disposed within a handle of a plasma arc torch through an activation member as previously set forth to activate the supply of gas to the plasma arc torch and further to terminate, or deactivate, the supply of gas.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.